1. Field of the Invention
The invention relates to apparatus for and methods of drilling holes through generally inaccessible structural members concealed within hollow walls and for pulling flexible lines through those holes.
2. Background Information
Flexible lines, such as electrical power wires or cables, telephone wires, coaxial video entertainment cables, fiber optic signal transmission lines, water lines (e.g., for a refrigerator""s ice maker), etc., can be relatively easily positioned within the walls of a building or above a ceiling of the building if those lines are installed after framing, but before the walls or ceilings are completed. This approach is customary for new construction. Once the structure has been completed, however, adding, replacing, or moving lines within a hollow wall, in a restricted crawl space above a ceiling or beneath a floor, is a much more difficult task.
In many remodeling or xe2x80x9cold workxe2x80x9d situations in single story residences a new line of some sort or another (e.g., a three conductor non-metallic sheathed electrical power cable) is run through an attic crawl space and down through a hollow wall to a service point (such as a point where an electrical outlet box is to be installed a foot or so above a floor, or a switch box located several feet above the floor). Ideally, to avoid damaging and replacing large portions of the wall surface, a job of this sort requires cutting or drilling a hole through the top plate of the wall, shoving the line through that hole and feeding it to a small access hole cut into the hollow wall. The necessary hole can be drilled from the attic and the line shoved down through the top plate only if there is adequate working clearance - e.g.., if the vertical distance between the top plate and closest roof truss, roofing panel or other obstacle above it is great enough that a workman can put an electric hand drill into position to drill through the top plate. If the service point is located on an exterior wall, this approach commonly fails completely because the vertical free space between the top plate and the lowest overhead roof member is too small. Moreover, even when there is working clearance, there is always a chance for the worker to drill the hole through the top plate between two adjacent wall studs and then find that access hole had been cut between two other walls studs, This commonly requires a second trip into the attic crawl space to drill another hole.
An additional problem arises if a conventional hollow wall contains a horizontal framing member located between the top plate and the sill. In these cases, even if one successfully feeds a line through the top plate of the wall, the presence of the additional framing member blocks the line from being dropped down to an outlet box located near the floor. Prior art practice in such cases generally requires cutting into and removing a portion of the wall in order to gain access to the additional horizontal member. This, of course, requires additional labor in patching the wall and restoring whatever decorative coating was on it before the job was started.
A number of US patents are notable among prior art references in this area, and were described in the parent application hereto. These references include:
U.S. Pat. No. 1,408,802, wherein Crocker et al. teach a flexible drill shaft turning within a flexible coaxial guide tube for use in drilling holes through a plurality of ceiling joists. Crocker et al. provide a collapsible and expandable guide device mounted behind the drill head. Their guide device is adapted to collapse when pushed through a hole in ajoist, and to expand under the influence of bias springs when free of the joists. When in its expanded configuration, the guide device acts to space the drill bit away from the upper surface of a ceiling by some preset amount, thus ensuring that each of a plurality of holes is made at the same distance above the ceiling. Crocker et al. do not teach an arrangement for ensuring that the holes drilled by their apparatus are drilled perpendicular to the joists.
U.S. Pat. No. 2,958,349, wherein McNutt teaches the use of a drill bit rotated by a flexible shaft encased in a rigid guide tube. The drill bit is translated toward the work through a bushing affixed adjacent one end of the guide tube.
U.S. Pat. Nos. 3,611,549 and 3,697,188, wherein Pope discloses a flexible-shafted drilling apparatus for forming holes in and installing lines through structural members concealed within hollow walls. Pope teaches the use of a drill bit having a throughhole transverse to the axis. A line or a line leader of some sort can be fed through the throughhole to attach the line to the drill bit, which is then pulled back towards the drill operator by means of the flexible shaft. Pope also teaches the use of a separate tool for guiding his drill bit into cutting contact with the concealed structural member.
U.S. Pat. No. 5,395,188, wherein Bailey et al. teach the use of a curved, rigid guide for positioning a drill bit attached to flexible shaft so as to drill an upwardly angled hole from a starting point near a floor to a finishing point within a hollow wall. Bailey et al. teach the use of their drill guide to drill through the wall and the wall sill or sole plate.
A preferred embodiment of the invention comprises a flexible guide tube having a work-engaging means adjacent a first end of the tube; means for bringing the work-engaging means into perpendicular engagement with an obstruction; and a drill, hole saw, or other cutting tool adapted to be inserted into the second end of the tube and pushed through the tube into cutting engagement with the obstruction. In this embodiment the work-engaging element is adapted to hold the tubular guide in a fixed position against the torsional, or other, forces of a drill or other cutting tool being rotated by means of a flexible shaft disposed within the guide tube so as to cut the throughhole in the obstruction.
Preferred embodiments of the invention use alignment means, such as a collared lead screw arrangement, to draw a cutting head into perpendicular alignment with a working surface. The collared lead screw is fed through a guide tube into operative contact with the working surface and is screwed into the working surface. The collar on the preferred screw is larger in diameter than an axial throughhole formed in a member of the cutting head assembly. In a preferred embodiment, the member having the axial throughhole is prohibited from rotating about the axis of the guide tube.
Another feature of a preferred embodiment of the invention is the combination of a flexible guide tube; a first cutting tool adjacent a first end of the tube and driven by a first flexible shaft to cut a throughhole through a first obstruction disposed within a hollow wall; and a second cutting tool adjacent the first end of the tube and driven by a second flexible shaft to subsequently cut a throughhole through a second obstruction disposed within or at the top or bottom of the hollow wall.
It is an object of a preferred embodiment of the invention to provide for fishing a large diameter flexible line, such as an electrical cable comprising three conductors of #12 AWG diameter, through a guide tube inserted into an access hole cut in a hollow wall and thence through a throughhole in an obstructing structural member. It is also an object of the invention to provide for fishing the large diameter flexible line through a throughhole in an obstructing structural member, into a guide tube aligned with that throughhole and thence to an access hole cut into a hollow wall.
It is a further objective of the invention to provide a method of and apparatus for working through an access hole in a hollow wall to cut a throughhole through an obstruction within the wall without damaging those portions of he wall immediately adjacent the access hole.
Although it is believed that the foregoing recital of features and advantages may be of use to one who is skilled in the art and who wishes to learn how to practice the invention, it will be recognized that the foregoing recital is not intended to list all of the features and advantages. Moreover, it may be noted that various embodiments of the invention may provide various combinations of the hereinbefore recited features and advantages of the invention, and that less than all of the recited features and advantages may be provided by some embodiments.